Compared with a conventional base station, a whole system of a distributed base station using remote radio technologies is divided into a baseband processing unit (BBU) and a remote radio unit (RRU). The RRU is placed at an access point far away from the BBU, the RRU and the BBU are connected through an optical fiber, and a baseband radio signal is transmitted in an analogue or digital manner.
Recently, a radio access network system based on a cloud computing technology, C-RAN (cloud RAN) gradually draws wide attention of the industry. In centralized access network architecture of the C-RAN, baseband signals of multiple RRUs are transmitted to a centralized BBU computing center through a transport network. The baseband signals are processed in the centralized BBU computing center so as to obtain benefits of statistical multiplexing and joint processing of computing resources, which puts forward a very high demand for a transmission bandwidth of the transport network. To effectively reduce the data transmission bandwidth demand of the RRU and the BBU computing center, a pair of compressing/decompressing modules may be deployed between the RRU and the BBU computing center. The baseband signal transmitted between the RRU and the BBU computing center is compressed at one end (e.g., local end), and after being transmitted through the transport network, the compressed signal is restored at a peer end, thereby greatly reducing the transmission cost of the network. Because additional delays are introduced due to operations such as compression/decompression and network transmission, these delays affect a process which has a high requirement for a round-trip delay in the system.
In the whole system, two processes which have the highest requirement for the delay are a random access process and a hybrid automatic repeat request process. Because window length of a random access response is settable, a delay of the random access process is easy to be satisfied. However, for a delay of the hybrid automatic repeat request process, additional delays introduced due to the compression/decompression, the network transmission and so on affect a feedback time for feedback information of uplink data, thereby causing timing sequence chaos for a hybrid automatic repeat request (HARQ) and unnecessary retransmission.